Method and apparatus for detecting the theft of articles

ABSTRACT

The theft of articles or goods maintained in a vending place such as a department store having at least one exit passageway is prevented by affixing thereto a preferably small detection element comprising a receiver of first predetermined frequency, a transmitter of second predetermined frequency, and power supply means coupled from said receiver and capable of disabling said transmitter. At the authorized checkout area of the store there is disposed a relatively high power transmitter of first predetermined frequency capable of preferably permanently disabling the power supply means and in turn said transmitter of second predetermined frequency of the detection element. In one preferred embodiment the power supply means includes a rectifier circuit which is destroyed (burned out and thus opened) when the detection element comes within predetermined proximity to the high power transmitter at the checkout area. At the exitway there is disposed a transmitter of first predetermined frequency and a receiver of second predetermined frequency which only detects a signal when the power supply means has not been disabled at the authorized checkout area whereby an alarm signal is generated.

United States Patent 1191 Hall et al. Jan. 7, 1975 [5 METHOD ANDAPPARATUS FOR 3,711,848 1 1973 Martens 340/280 DETECTING THE THEFT 05*ARTICLES 3,713,133 1/1973 Nathans.... 340/224 X 3,720,940 3/1973 Fox340/280 X [75] Inventors: Roger L. Hall, Francestown;

Edward famwnght, Nashua 1 Primary Examiner-Glen R. Swann, Ill 22 fClarkson, Attorney, Agent, or Firm-Wolf, Greenfield & Sacks nas e, as

[73] Assignee: North American Systems Corp., [57] ABSTRACT f 'l by SamHall The theft of articles or goods maintained in a vending andwamwl'lght place such as a department store having at least one [22]Filed; Inez/5,1972 exit passageway is prevented by affixingthereto apreferably small detection element comprising a re- 1 PP N0: 266,130ceiver of first predetermined frequency, a transmitter of secondpredetermined frequency, and power supply 52 us. CI 340/280, 340/224,343/6.8 R w cqupled m Said receiver and m 511 1m. 01. G08b 13/22 ablmgSaid transmllter- A E authomeicheckgtut 58 Field of Search 340/258 R,280, 224; area of the Store there IS deposed a relatively hlgh 325/16,21 135, 343/63 R power transmitter of first predeternrmed frequencycapable of preferably permanently disabling the power v 5 ReferencesCited supply means and in turn said transmitter of second UNITED STATESPATENTS predetermined frequency of the detection element. In onepreferred embodiment the power supply means 2,241,283 7/l358 l-lallden325/l85 UX includes a rectifier circuit which is destroyed (burned 1 331y fig out and thus opened) when the detection element 3088l06 4/1963 icomes within predetermined proximity to the high H1967 'ix'j powertransmitter at the checkout area. At the exit- 3,418,655 12/1968 Baylorway there is disposed a transmitter of first predeter- 3,493,955 2/1970Minasy mined frequency and a receiver of second predeter- 3,546,69512/1970 Freedman.... 343/6.8 X mined frequency which only detects asignal when the 3,582,931 6/1971 Nawrocki 340/280 X power supply meanshas not been disabled at the auf g l thorized checkout area whereby analarm signal is c inc cy 3,685,050 '8/1972 Cartwright... 343/6.8 xgenerated 3,707,711 12/1972 Cole 340/280 6 Claims, 7 Drawing FiguresFRFNEMIFEFTEI I I I I 24 I 1 I J I C3 I g 02/5 I IL I 11.2 Y I 36 I I 01 I I L M F 7 J 1 1 SZ 4. c1 1.1; I I l I L E EDEE 3L 1 Patented Jan. 7,1975 2 Sheets-Sheet 2 TRZRISTAITTEFTE I l l I l g I I C3 g 02;; IL .L2 5ix Y I 2 l I I L .E I

MODULATOR T a V V y REcEIvER POWER I- TRANSMITTER RI SUPPLY f T2TRANSMWTER ARTICLE RECEIVER DEMODULATOR ACCUMULATOR TI R2 4 2 iifF/a' 5METHOD AND APPARATUS FOR DETECTING THE THEFT OF ARTICLES FIELD OF THEINVENTION The present invention relates in general to an apparatus orsystem and associated method of detecting the theft of articles from avending place such as a department store. More particularly, the presentinvention is directed to the type of system that employs an electronicdetection element preferably of small integratedcircuit size affixed tothe article or goods.

BACKGROUND OF THE INVENTION Many different means have been devised forpreventing or deterring the theft of articles or goods from a store orother vending place. Some of these means include mirrors, securitypolice, cameras, television with video recording and gentian violetmarking. None of these means are completely effective, and once thethief has been able to conceal the item these above devices cannotdetect the passage of the item through the exitway of the store.

The problem of stolen merchanidse is further complicated by the possiblelegal rights of the individual against false accusations. Thus, personsin authority at the store are hesitant to accuse any potential thief,'inthe absence of effective detection means, for fear of the possibility ofa suit for defamation of character being filed. Also, any falseaccusations may have a deleterious outcome regarding the good-will ofthe store.

Accordingly, it is important that the detection means accuratelyidentify, preferably at the exitway of the store, articles that have notpassed through the checkout counter and been paid for. In the past therehave been both electrical and mechanical devices designed. Generally,however, these devices are too costly, too dangerous, or too unreliable.One technique, for example, shown in U.S. Pat. No. 3,582,931 uses aradioactive material affixed to the article. The problem with thistechnique is that the articles carrying the material may be adverselyaffected by the presence of any radioactive material. Another techniqueis to use a sensitive reed switch (see US. Pat. No. 3,577,136 which isresponsive to a magnet disposed at the exitway. This type of adevicehas, inter alia, the disadvantage that it can be too easily falselytriggered. Still another prior art device is of the resonant frequencytype (see U.S. Pat. Nos. 3,493,955 and 3,500,373) wherein a resonantcircuit is affixed to the article and a receiver/transmittercombination. is used to monitor changes in the ambient energy level dueto the presence of the resonant circuit. This device also is susceptibleto false triggering because the frequency sensitivity of the energylevel monitoring equipment is quite low and metal objects can causefalse triggering.

OBJECTS OF THE INVENTION Accordingly, it is an important object of thepresent invention to provide an improved apparatus or system andassociated method for detecting the theft or articles or goods from avending place such as a department store. The apparatus of the presentinvention is of the electromagnetic wave detection type.

Another object of the present invention is to provide a system forpreventing article thefts that is both safe and effective in operation.With the apparatus of the present invention there is no exposure toharmful radiation.

A further object of the present invention is to provide an apparatus formonitoring the unauthorized passage of articles'past a predeterminedcheckpoint preferably adjacent an exitway of the store wherein there isno need for additional security personnel and wherein the apparatus isreadily concealable from the view of the ordinary purchaser.

Still another object of the present invention is to provide a system forpreventing article thefts that effectively distinguishes between theauthorized and unauthorized passage of articles past a given checkpointthereby alleviating the false alarm problem.

An additional object of the present invention is to provide a detectionelement that readily impregnates or adheres to various articles whetherconstructed of paper, cloth, wood, plastic, etc. that is very small insize, and that may be easily disabled [by even non-skilled workers.

SUMMARY OF THE INVENTION To accomplish the foregoing and other objectsof the invention, there is provided a system for detecting theunauthorized removal of articles from an enclosure such as a departmentstore having a checkout area and a passageway through which the articlesare generally moved from the enclosure. The system comprises atransmitter of a first frequency and] a receiver of a second frequencyboth being disposed at the exit passageway. The receiver of secondfrequency is not responsive to a signal of first frequency. A means isalso provided for establishing an alarm condition when the receiver atthe passageway receives a signal of second frequency.

A relatively small detection element is attached to the article andcomprises a receiver of first frequency, a transmitter of secondfrequency and means responsive to a signal, of a level less than apredetermined threshold level, from said receiver of a first frequencyfor providing power to the transmitter of a signal of second frequency.

If the article'is properly taken from the enclosure it passes through acheckout area where there is located a high power transmitter of a firstfrequency for estab lishing a signal of a level greater than thepredetermined threshold level from the receiver of the detection elementto thereby disable the power providing means, interrupting power to thetransmitter of the detection element. Thereafter, when the detectionelement passes through the exit passageway the receiver of secondfrequency disposed at the exit passageway does not receive a signalbecause of the permanently disabled power providing means and thereforeno alarm cpndition is established. Alternatively, if the article doesnot pass as it should through the checkout counter area and is notsubjected to the high power transmitter disposed thereat, the means forproviding power to the transmitter of the detection element is notinhibited and thus as the article passes through the exit passageway thereceiver disposed at the passageway will receive a signal of a secondfrequency and thus there will be an alarm condition established.

In accordance with another aspect of the present invention thetransmitter of a second frequencywhich forms part of the detectionelement has a modulation means associated therewith. Each of themodulation means is different for each type of article being protected.By using a first frequency transmitter and second frequency receiverjust before the checkout area, it is possible to keep track of allarticles passing to the checkout area for purposes of inventory control.For this purpose it is also necessary to have some type of accumulatorfor distinguishing each article and providing a cumulative count of eacharticle sold.

BRIEF DESCRIPTION OF THE DRAWINGS Numerous other objects, features andadvantages of the invention should now become apparent upon a readingof. the followingdetailed description taken in t conjunction with theaccompanying drawings in which:

FIG. 1 is a schematic diagram showing the different areas of the storeand the components of the present invention associated therewith;

FIG. 2A shows a block diagram of the detection element of the presentinvention;

FIG. 2B shows a block diagram of the means provided at the checkout areaof the store;

FIG. 2C is a block diagram of the means provided at the exitway area ofthe store;

FIG. 3 is a circuit diagram of a preferred embodiment of the detectionelement shown in FIG. 2A;

FIG. 4 shows a block diagram of an alternate embodiment for thedetection element; and

FIG. 5 is a block diagram of the inventory monitoring means of thepresent invention used in conjunction with the detection element of FIG.4.

DETAILED DESCRIPTION FIG. 1 shows the three basic areas of a store thatare of interest in discussing the concepts of the present invention.Various articles are disposed in storage or display area in any knownmanner and preferably each article A has a detection element affixedthereto. FIG. 2A which is discussed in more detail hereinafter shows ablock diagram of one detection element of this invention. If the articleis being properly purchased it passes from area 10 to checkout area 12where there is usually disposed a checkout counter '14 and associatedcash register 16 or the like. The high power transmitter of the presentinvention is disposed at the checkout area 12 for disabling thedetection element and permitting passage of the article through theexitway area 14 without providing an alarm. This high power transmittermay be disposed beneath the recess 18 provided in counter-top 20 ofcheckout counter 14. A pair of doors 21 is shown in FIG. 1 for providingfinal access to the outside of store or enclosure 22.

If the article A has not passed through the checkout area 12 and has notbeen subjected to the high power transmitter thereat, when the articledoes pass through the doors 21 means are provided adjacent thereto asdiscussed with reference to FIG. 2C for providing an alarm.

Referring now to FIG. 2A there is shown a block diagram of the detectionelement 24 which is affixed to article A in an appropriate manner. Thisdetection element 24 is preferably constructed by integrated circuittechnology and may be no larger than 0.025 sq. in. The detection element24 includes an input antenna 26 which couples to receiver R1. ReceiverR1 is preferably a fixed frequency receiver of frequency Fl which may beon the order of 460 megacycles. The detection element 24 also includes atransmitter T2 (and associated antenna 27), and a power supply 30coupled from receiver R1 for delivering power to both receiver R1 andtransmitter T2 when an input signal of frequency F1 is received onantenna 26. Transmitter T2 may be of conventional design. Power supply30 which is discussed later with reference to FIG. 3 preferably includesa rectifier that is preselected so that if a power greater than apredetermined threshold is received by receiver R1 the rectifier of thepower supply 30 is burned out (opened) and thus when any future signalis received by receiver R1 the power supply 30 blocks power totransmitter T2 and prevents any transmission of its associated frequencyFZ. Frequency F2 may be on the order of 430 megacycles.

FIG. 2B shows the checkout area 12 and the transmitter 32 which is ahigh power transmitter capable of generating sufficient energy when thearticle is passed over the transmitter to cause the rectifier of powersupply 30 to be opened.

In FIG. 2C there is shown the exitway area 14 including a transmitter T1(with associated antenna 28) of first frequency F1 and a receiver R2(with associated antenna 29) of second frequency F2 having an alarm 34associated therewith for generating an alarm signal when a signal offrequency F2 is received by receiver R2. If the article has beenappropriately passed through checkout area 12 and passes as shown inFIG. 2C between transmitter T1 and receiver R2 the signal fromtransmitter T1 is blocked because the rectifier of power supply 30 hasprevented transmission of any F2 frequency, and thus receiver R2 doesnot trigger alarm 34.

Referring now to FIG. 3, there is shown a circuit diagram for oneembodiment of the detection element 24 shown in a block diagram in FIG.2A. The detection element 24 comprises a receiver R1, a transmitter T2,and power supply 30. The receiver R1 includes a tank circuit comprisedof capacitor C1 and an inductor L1. Similarly, transmitter T2 includes atank circuit comprised of capacitor C2 and inductor L2. The inductors ofthese tank circuits function as the antennas of each tank circuit.

The power supply means 30 comprises transistor Q1, diode D1, capacitorsC3 and C4 and ressistor R. The collector of transistor Q1 couples totransmitter T2 and the emitter of transistor Q1 couples by way of adiode D1 to receiver R1. Capacitor C3 also couples from the emitter oftransistor 01 to both receiver R1 and transmitter T2. Resistor R andcapacitor C4 are coupled, in parallel, from the base of transistor O1 totransmitter T2. Resistor R establishes the proper bias for the base oftransistor 01 and capacitor C4 is an AC bypass capacitor. It is thediode D1 that is destroyed when receiver Rl receives a signal ofstrength greater than a predetermined threshold level. This level is afunction of the type diode selected. When diode D1 is burned outtransistor Q1 can no longer supply power to either receiver R1 ortransmitter T2.

Because the receiving and transmitting antennas (inductors L1 and L2,respectively) are much smaller than a half wave, an optimum inpedancematch has been calculated at the terminals of the antenna, ofapproximately 73 ohms. By chosing a five microfarad capacitor forcapacitor C1 and assuming a resonant frequency of 460 MHZ for receiverR1, an inductance of approximately 6,000 y. henries can be calculatedfor inductor L1. A loop of wire whose radius is 1/50 inch and whosethickness is 4 X l0" inch can be used for inductor L.

Using the same value of capacitance for capacitor C2 the inductance inthe transmitter can be calculated to be approximately 5,800 up. henries,assuming that the transmitter T2 has a resonant frequency on the orderof 430 MHZ.

Thus, when the receiver R1 is receiving a signal of frequency F1, diodeD1 rectifies the output from the tank circuit of receiver R1andtransistor Q1 provides power by way of capacitor C3 to both receiverR1 and transmitter T2. A feedback line 36 couples from transmitter T2 tocapacitor C4 for providing regenerative feedback to the power supplymeans 30. When the circuit shown in FIG. 3 is passed adjacent thetransmitter 32 shown in FIG. 2, the power from the transmitter 32 whichis received by receiver R1 is sufficient to burn out diode D1, therebyinhibiting the power supply means 30 and the transmitter T2 shown inFIG. 3. When the article is subsequently passed through the exitway area14 shown in FIG. 2C the transmitter T2 is not capable of sending anysignal to receiver R2 at the exitway area and thus no alarm condition isgenerated. If the circuit of FIG. 3 is not subjected to the high powertransmitter 32 the diode D1 is not burned out and thus transmitter T2 iscapable of generating a signal received by receiver R2 at the exitwayarea 14 for generating an alarm condition by means of alarm 34.

Referring now to FIG. 4 there is shown a block diagram of anotherembodiment of a detection element of 24. The block diagram of FIG. 4 issimilar to the previous block diagram of FIG. 2A with the addition of amodulator 40 which receives an input from power supply 30 and has anoutput connected to transmitter T2. Modulator 40 may be of conventionaldesign. When receiver R1 receives a signal of frequency F1, power supply30 provides power to receiver R1, transmitter T2 and modulator 40, andthe output signal from the antenna associated with transmitter T2 is amodulated frequency signal. A-known type of amplitude modulation can beprovided by modulator 40. With the use of the detection element of'FIG.4 the exitway detection circuitry may be similar to that shown in FIG.2C with the addition of a demodulator associated with receiver R2.

FIG. 5 shows a block diagram of an inventory monitoring means which maybe disposed before or after the checkout area 12 (see FIG. 1). Theinventory monitoring means may be used in conjunction with the highpower transmitter 32 at the checkout area 12. The purpose of thisinventory control means is to provide a running total of the number oftotal articles of each type that have been passed through the checkoutarea 12. By determining the total amount sold the total inventory onhand can be easily calculated.

The block diagram of FIG. 5 is similar to the one shown in FIG. 2C andcomprises a tranmitter T1, a rece iver'R2, a demodulator 42, and anaccumulator 44. As the article A passes between the transmitter T1 andreceiver R2, a modulated signal from transmitter T2 of the detectionelement shown in FIG. 4 is coupled to receiver R2. The demodulator 42demodulates this signal, thereby in effect identifying the particulararticle being sold, and an accumulator 44 provides a total of theparticular article that has been sold over a part predetermined timeperiod. The modulator 42 and accumulator 44 may both be of conventionaldesign and would include various electronics components. Accumulator 44may even be a general purpose digital computer. Also, the apparatusshown in FIG. 5 may replace the detection circuitry of FIG. 2C in oneparticular system.

In accordance with another aspect of this invention the transmitter Tlmay have a modulator associated therewith (see FIG. 2C), in which casereceiver R1 would have a demodulator associated therewith for enablingoperation of power supply 30 (see FIG. 2A).

Having described some embodiments of the present invention, it shouldnow become obvious that there are numerous other embodiments andmodifications thereof all of which should fall within the spirit andscope of the present invention as defined by the appended claims.

What is claimed is:

l. A system for detecting the unauthorized removal of articles from anenclosure having a checkout area and a passageway through which saidarticles may be moved, said system comprising;

a transmitter of a signal of first signal characteristic disposed atsaid passageway,

a receiver of a signal of second signal characteristic disposed at saidpassageway and being nonresponsive to a signal of first signalcharacteristic,

means for establishing an alarm condition when said receiver receives asignal of second signal characteristic,

a detection signal attached to the article and comprising a receiver ofa signal of first signal characteristic, a transmitter of a signal ofsecond signal characteristic, and means responsive to a signal, of alevel less than a predetermined threshold level, from said receiver of asignal of first signal characteristic for providing power to saidtransmitter of a signal of second signal characteristic,

a power transmitter of a signal of first signal characteristic disposedat said checkout area for establishing a signal of a level greater thansaid predetermined threshold level from said receiver of a signal offirst signal characteristic to thereby inhibit the providing of power tosaid transmitter of a signal of second signal characteristic when saidarticle is at said checkout area,

whereby said receiver of a signal of second signal characteristicreceives a signal to thereby establish an alarm condition when anunauthorized removal of said article has occurred, and does not receivea signal when an authorized removal has occurred,

said receiver of first characteristic comprising a tank circuit and saidtransmitter of said second characteristic comprising a tank circuit,said power providing means including a transistor having an inputelectrode and an output electrode,

means for biasing the transistor including a resistor coupled to the'input electrode of the transistor, a diode coupling from the outputelectrode of the transistor to one of the tank circuits and capacitancemeans coupling from the output electrode of the transistor to both tankcircuits,

each said tank circuit including an inductor defining part of the tankcircuit and forming an antenna means for transmitting or receivingsignals.

2. The system of claim 1 comprising a demodulator 5 associated with saidreceiver of a signal of second signal characteristic.

3. The system of claim 2 comprising means positioned adjacent thecheckout area for registering a total count of each article passingthrough the checkout 6. The system of claim 1 wherein said detectioneleareament comprises a modulator coupling to said transmit- 4. Thesystem of claim 3 wherein said means for registering includes anaccumulator means.

5. The system of claim 1 wherein the anode of said 5 diode couples tothe output electrode and the cathode provldmg means of Sald dfitectlonelementof said diode connects to the receiver tank circuit.

ter ofa signal of second signal characteristic and means for couplingpower to said modulator from said power

1. A system for detecting the unauthorized removal of articles from anenclosure having a checkout area and a passageway through which saidarticles may be moved, said system comprising; a transmitter of a signalof first signal characteristic disposed at said passageway, a receiverof a signal of second signal characteristic disposed at said passagewayand being non-responsive to a signal of first signal characteristic,means for establishing an alarm condition when said receiver receives asignal of second signal characteristic, a detection signal attached tothe article and comprising a receiver of a signal of first signalcharacteristic, a transmitter of a signal of second signalcharacteristic, and means responsive to a signal, of a level less than apredetermined threshold level, from said receiver of a signal of firstsignal characteristic for providing power to said transmitter of asignal of second signal characteristic, a power transmitter of a signalof first signal characteristic disposed at said checkout area forestablishing a signal of a level greater than said predeterminedthreshold level from said receiver of a signal of first signalcharacteristic to thereby inhibit the providing of power to saidtransmitter of a signal of second signal characteristic when saidarticle is at said checkout area, whereby said receiver of a signal ofsecond signal characteristic receives a signal to thereby establish analarm condition when an unauthorized removal of said article hasoccurred, and does not receive a signal when an authorized removal hasoccurred, said receiver of first characteristic comprising a tankcircuit and said transmitter of said second characteristic comprising atank circuit, said power providing means including a transistor havingan input electrode and an output electrode, means for biasing thetransistor including a resistor coupled to the input electrode of thetransistor, a diode coupling from the output electrode of the transistorto one of the tank circuits and capacitance means coupling from theoutput electrode of the transistor to both tank circuits, each said tankcircuit including an inductor defining part of the tank circuit andforming an antenna means for transmitting or receiving signals.
 2. Thesystem of claim 1 comprising a demodulator associated with said receiverof a signal of second signal characteristic.
 3. The system of claim 2comprising means positioned adjacent the checkout area for registering atotal count of each article passing through the checkout area.
 4. Thesystem of claim 3 wherein said means for registering includes anaccumulator means.
 5. The system of claim 1 wherein the anode of saiddiode couples to the output electrode and the cathode of said diodeconnects to the receiver tank circuit.
 6. The system of claim 1 whereinsaid detection element comprises a modulator coupling to saidtransmitter of a signal of second signal characteristic and means forcoupling power to said modulator from said power providing means of saiddetection element.